Fuel atomizing nozzles for use in gas turbines and the like commonly employ compressed air to atomize the fuel. It is also well known to employ fuel swirl chambers to produce a hollow conical form of spray. These features may be combined as disclosed in U. S. Pat. No. 3,474,970 in which compressed air is fed around the outside of an extended conical discharge orifice of a swirl chamber to atomize the conical sheet of fuel emerging from the edge of the discharge orifice. It is also well known to introduce compressed air to the inside of a fuel swirl chamber to obtain mixing of the fuel and air in order to improve atomization. A disadvantage of both of such devices is that the quantity of air which can be brought into intimate contact with the fuel is limited by geometric considerations; in the first case because the air and fuel sheets necessarily have to follow approximately parallel directions, and in the second case because the discharge orifice size is limited by the hydraulic design considerations especially if, as is usually the case, the resultant spray cone angle must be held to a desired value. As a result, in both cases insufficient air can be utilized to obtain satisfactory atomization under all conditions particularly those of high fuel flow rates and/or high fuel viscosity.
Economic and supply considerations are at present dictating the use of fuels of lower quality and higher viscosity than heretofore and, hence, it is important to obtain good fuel atomization in order to satisfy general requirements for both fuel economy and atmospheric pollution standards.